Field of the Invention
The present invention relates to a sheet stacking apparatus configured to have sheets stacked thereon, and an image forming apparatus including the sheet stacking apparatus.
Description of the Related Art
Hitherto, a sheet feed cassette including a sheet stacking member disposed elevatably so that stacked sheets can be pressed against a sheet feed roller and a regulating member configured to regulate an end portion of the sheets stacked on the sheet stacking member has been proposed.
Japanese Patent Application Laid-Open Publication No. 8-53232 discloses a sheet feed cassette including a width regulating member configured to regulate an end portion of a sheet in a width direction, a conveyance direction regulating member configured to regulate an end portion of the sheet in a length direction (longitudinal direction), and a sheet stacking member capable of pivoting with respect to a housing. The width regulating member and the conveyance direction regulating member are disposed movably to correspond to sheet sizes, and the sheet stacking member is configured so as not to interfere with the width regulating member and the conveyance direction regulating member.
Recently, there are increasing demands for inexpensive and small-sized printers or copying machines that can be installed in offices or at home, and so it is desirable to further reduce costs and realize downsizing of sheet feed cassettes disposed in such printers and copying machines. Along with the downsizing of the image forming apparatuses, it is required for the sheet feed cassettes to cope with a greater variety of sheet sizes. Furthermore, there are demands to enhance the performance of conventional printers and machines regarding reproducibility of images printed on the sheets (printing precision).
According to the sheet feed cassette disclosed in Japanese Patent Application Laid-Open Publication No. 8-53232, the housing must be increased in size in order to enable use of sheets having a larger size compared to the conventional sheets, and as a result, the whole apparatus had to be increased in size. On the other hand, in order to enables sheets having a smaller size compared to the conventional sheets to be used, the width regulating member and the conveyance direction regulating member must be downsized to prevent the width regulating member and the conveyance direction regulating member from interfering with the sheet stacking member.
However, when the width regulating member and the conveyance direction regulating member are downsized, the contact area between the end portion of the sheet and the width regulating member or the conveyance direction regulating member is reduced. Therefore, the accuracy of positioning the sheets is deteriorated, and especially when sending large sized sheets from the sheet feed cassette, the amount of skewing caused in the sheets is increased. The increase in the amount of skewing of the sheets leads to deteriorated printing precision.